linux-kernel - Re: [PATCH] mm/THP: use hugepage_vma_check() in khugepaged_enter_vma

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Message-ID: <alpine.DEB.2.21.1805211419210.41872@chino.kir.corp.google.com>
Date:   Mon, 21 May 2018 14:19:31 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Song Liu <songliubraving@...com>
cc:     linux-mm@...ck.org, kernel-team@...com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/THP: use hugepage_vma_check() in
 khugepaged_enter_vma_merge()

On Mon, 21 May 2018, Song Liu wrote:

> khugepaged_enter_vma_merge() is using a different approach to check
> whether a vma is valid for khugepaged_enter():
> 
>     if (!vma->anon_vma)
>             /*
>              * Not yet faulted in so we will register later in the
>              * page fault if needed.
>              */
>             return 0;
>     if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
>             /* khugepaged not yet working on file or special mappings */
>             return 0;
> 
> This check has some problems. One of the obvious problems is that
> it doesn't check shmem_file(), so that vma backed with shmem files
> will not call khugepaged_enter().
> 
> This patch fixes these problems by reusing hugepage_vma_check() in
> khugepaged_enter_vma_merge().
> 
> Signed-off-by: Song Liu <songliubraving@...com>

Acked-by: David Rientjes <rientjes@...gle.com>